What is the role of the ciliary muscles in enabling the eye to see both nearby and distant objects clearly?
Generated by claude-sonnet-4-6 · 2026-06-26 01:06 · grounding rag
Model Answer
Ciliary muscles control the curvature of the eye lens, thereby adjusting its focal length — this ability is called accommodation.
- For distant objects: Ciliary muscles relax, the lens becomes thin, and its focal length increases. This focuses the image of distant objects clearly on the retina.
- For nearby objects: Ciliary muscles contract, the lens becomes thicker (curvature increases), and its focal length decreases. This focuses the image of nearby objects clearly on the retina.
Thus, by continuously adjusting the lens shape, ciliary muscles enable the eye to see both nearby and distant objects clearly.
Source: Chapter 10, Section 10.1.1 – Power of Accommodation
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Explanation
- The examiner wants three clear points: (1) what ciliary muscles do, (2) action for distant vision, (3) action for near vision. Each is worth ~1 mark.
- Use the key terms: relax/contract, thin/thick, focal length increases/decreases — these are the exact words from the textbook and earn full marks.
- The word accommodation should appear — it is the technical term for this property.
- Do not mix up: relaxed = thin lens = long focal length = distant objects; contracted = thick lens = short focal length = nearby objects. This is a common error students make in exams.